1. Field of the Invention
Example embodiments of the present application relate to a system and method for telecommunications. More particularly, example embodiments are directed to system and methods of pre-registration, storing of pre-registered session information and session transfer, which may occur when an access terminal is in close proximity to a border area between a first radio access technology (RAT) area and a second RAT area.
2. Background Information
If an access terminal is capable of communicating using more than one RAT, the access terminal may travel across a border between a first coverage area operating according to a first RAT and a second coverage area operating according to a second RAT.
Examples of the Radio Access Technologies (RATs) are CDMA 2000 3G1X, High Rate Packet Data (HRPD), Long Term Evolution (LTE), Worldwide Interoperability for Microwave Access (WiMAX), ultra mobile broadband (UMB), etc.
When the access terminal reaches the border area and crosses the border area into a new RAT, a hand-off is conducted. Prior to the hand-off, in a pre-registration zone located between a first coverage area having a first RAT and a second coverage area having a second RAT, a pre-registration or re-registration is performed between the access terminal and an access network in order to ensure hand-off can take place in a suitable and timely manner so that wireless communication services for the access terminal is not interrupted. The pre-registration and re-registration generates pre-registration and re-registration session information, respectively. Conventionally, if the access terminal exits the pre-registration zone, the pre-registration and/or re-registration session information is deleted within the access terminal and the access network.
FIG. 1 illustrates a wireless communication system. In particular, the left hand side of FIG. 1 illustrates a long term evolution (LTE) coverage area and the right hand side of FIG. 1 illustrates a high rate packet data (HRPD) coverage area. Further, FIG. 1 illustrates a border area (i.e., a pre-registration zone) located in between the LTE coverage area and the HRPD coverage area. This border area is an area in which an access terminal (AT) may be triggered to perform a pre-registration process. A conventional pre-registration process includes the initial session registration (e.g. UATI request/assign in HRPD), radio connection set up (e.g. connection request and traffic channel assignment in HRPD), and session negotiation (e.g. radio link parameter negotiations and upper layer signaling and negotiations).
Still further, FIG. 1 illustrates that the HRPD coverage area includes a first subnet Subnet 1 and a second subnet Subnet 2. Accordingly, the pre-registration zone is divided into a first subnet pre-registration zone and a second subnet pre-registration zone. Lastly, FIG. 1 illustrates an example path that an access terminal AT may follow. This path is illustrated in FIG. 1 as including four points of interest identified as A, B, C, and D.
One skilled in the art will appreciate that the LTE coverage area, pre-registration zone and HRPD coverage area of the wireless system illustrated in FIG. 1 include a plurality of cells, and each of the plurality of cells may be covered by one or more RATs. For example, the cells of the LTE coverage area are supported by one or more access networks operating consistent with the LTE RAT, and the cells of the HRPD coverage area are supported by one or more access networks operating according to an HRPD RAT. Further, the cells within the pre-registration zone are supported by one or more networks operating consistent with the LTE RAT and possibly one or more networks operating consistent with the HRPD RAT.
Referring to FIG. 1, if the access terminal AT is at an edge of the LTE coverage area, one or more access networks may indicate to the access terminal that a current sector is a non-interference-limited border by providing a border indication broadcast by one or more access networks. In response to this border indication, the access terminal becomes aware of entering the border area, referred to hereinafter as the pre-registration zone.
If the access terminal enters the pre-registration zone, the access terminal may be triggered to perform pre-registration. Generally, pre-registration involves negotiating a pre-registration session at the target network of different RAT through a current serving technology air interface. In the example illustrated in FIG. 1, the pre-registration involves negotiating a pre-registration session with a HRPD access network (AN) of the HRPD coverage area using a technology air interface of the LTE coverage area.
Still referring to FIG. 1, at point A along the access terminal path, the access terminal receives a border indication broadcast from one or more LTE access networks and/or one or more HRPD access networks. In response to this indication, the access terminal begins a pre-registration process.
Pre-registration is generally required before a handoff can take place between the LTE coverage area and the HRPD coverage area. The handoff will take place once the access terminal crosses the LTE/HRPD coverage boundary indicated in FIG. 1 and enters the second subnet Subnet 2 of the HRPD coverage area. Once this idle handoff takes place, the access terminal is supported by one or more HRPD access networks of the HRPD coverage area.
Still referring to FIG. 1, the access terminal then crosses back into the pre-registration zone. In particular, the access terminal AT reenters the second subnet of the pre-registration zone. Still following the access terminal path, the access terminal exits the pre-registration zone and reenters the LTE coverage area. Because this application is concerned primarily with the transition from the LTE coverage area to the HRPD coverage area, details regarding the access terminal transitioning from the HRPD coverage area back into the LTE coverage area is omitted herein for the sake of brevity.
Further, the access terminal then reenters the second subnet of the pre-registration zone at point B of the access terminal path. According to conventional pre-registration techniques, at point B, the access terminal AT will again pre-register with the HRPD coverage area. This second pre-registration may be referred to as a re-registration. This second pre-registration or re-registration is necessary according to conventional techniques because the information related to the first pre-registration is deleted from both the access terminal and the access networks of the LTE coverage area and the HRPD coverage area. One skilled in the art will appreciate that each pre-registration requires time and resources. For example, each pre-registration requires enablement of a traffic channel at the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and partial or full session negotiations through an air interface of the E-UTRAN.
Still following the access terminal path of FIG. 1, the access terminal then transitions from the second subnet of the pre-registration zone into the first subnet of the pre-registration zone at point C. This transition requires a session transfer from the second target subnet of the different RAT to the first target subnet of the different RAT. The access terminal then reenters the LTE coverage area as illustrated in FIG. 1. Lastly, the access terminal AT again reenters the first subnet of the pre-registration zone at point D and thus, must again pre-register or re-register with the HRPD coverage network according to conventional practice. In addition, if the access terminal is ping-ponging at the border of different pre-registration zones, excessive session transfer requests will be sent at the air interface to occupy a large amount of radio resources and the excessive session transfer between different subnets will also create a large amount of unnecessary backhaul traffic.
As detailed above, according to conventional practices and/or a straight forward approach, a conventional access terminal following the path illustrated in FIG. 1 must perform pre-registration three different times, i.e., at points A, B and D. Each of these pre-registrations requires time and network resources.